The long-term goals of this proposal are to elucidate the failure of hepatocyte volume regulation during chronic ethanol ingestion, which results in hepatomegaly. Liver enlargement in turn leads to portal hypertension, impaired microcirculation, and anoxic degeneration of hepatic function. The immediate goal is to determine whether chronic ethanol ingestion in mice or acute administration of ethanol to hepatocytes in primary culture diminishes the capability of liver cells to regulate their volume. The project will utilize a novel, electrophysiological technique to measure change in hepatocyte water volume. The specific aims are 1) to determine the membrane water permeability coefficient for hepatocytes in primary culture and whether it is affected by ethanol; 2) to determine whether hepatocytes in primary monolayer culture regulate their volume in response to perturbations in external osmolality and whether volume regulation diminishes with chronic and acute effects of ethanol; 3) to determine whether rapid volume regulation in cultured hepatocytes facilitates secondary active transport of L-alanine by compensating for the osmolality of accumulated organic solute and whether this diminishes due to ethanol; 4) to determine whether passive, redistribution of cellular Cl- is voltage-driven by osmotically-induced changes in cell transmembrane potential, which constitutes a novel means for control of cell volume. Successful completion of this project will expand our knowledge of the mechanisms of hepatocyte volume regulation. Moreover, the health-relatedness of these studies will be the generation of new information on how chronic and acute effects of ethanol inhibit hepatocyte volume regulation, which in turn results in cell hypertrophy, hepatomegaly, and the sequelae of deteriorated hepatic function.